Protect

sounds like one or more speaker cables are either shorting or not connecting...I know you have checked all cables, but if it was defo ok in the other room, theres not much more that can be wrong. (i'm assuming that you turned the device off before dicsonnecting everything).

If you are using the same speakers, did a speaker get damaged in transit?

you can test your speaker cables and speakers with a basic Ohm meter..disconnect each speaker connection from the unit and test for resistance..should read similar ohms to what your speakers are (usually 6-12 ohms in home hifi). if any connection gives a significantly higher or lower reading, thats that culprit.